IMovie Export Problems - PLEASE HELP !!

Question

I have assembled a 3 hour movie in iMovie. I have tried to export approx. 20 times with no success. I have duplicated and renamed the project - deleting the original, this still does not work. I attempted to use Screenflow to record the movie playing in full screen playback - the playback crashes approx 20 mins in. I have tried to play the project within iMovie and record the preview screen (on largest size available) and it crashes approx 30 mins in. I am in despair as I have worked on the content of the movie for approx 2 years.
Tech Info
I have upgraded to Mountain Lion during the creation of the movie.
I have updated iMovie when updates are available.
I have 12GB RAM on board.
Hard Drive (1TB) is has approx 280GB free.
iMac - Oct 2011 - 27"
Really appreciate it if someone could help. Obviously I will not bin the project but am definitely looking for an easier fix than recreating the entire movie as I do not know if this is possible, both technically and mentally with the time that was put in already.
Thanks in advance

Answer 1

If you have Time Machine running, turn it off whenever you are exporting a project (and remember to turn it back on after the export is complete).
Additionally, try splitting the project into two parts (or maybe three or more). Keep the duplicate you created earlier from the original so that you have at least one full copy of your project intact. Now create two (or more) duplicates and rename them appropriately (such as My Project Part 1, My Project Part 2 and so forth).
Delete the second half from the first duplicate (My Project Part 1). Delete the first half from the second duplicate (My Project Part 2). If you created three or more duplicates, then break them up into the relevant segments by deleting appropriate sections.
Now try to export one project at a time. Hopefully, iMovie will be able to handle the shorter projects. If one of the projects fails to export, there may be a corruption in that project file. Splitting that project further may help to isolate the problem.
You may, of course, end up with several exported project files (movies), but at least you will have something for your efforts. If your intention is to burn a DVD, you can include them as separate movies on the DVD, but bear in mind that for a single layer DVD the total running time is limited to 2 hours when using iDVD (including menus). If publishing to the web, you could upload them as separate "episodes" or the like.
TIP: When splitting up the project into shorter sections, you could add an appropriate title to the end and/or beginning of each section before exporting (such as, "End of Part One" and "Part Two" etc.) to avoid an abrupt end or start for each section.
John